1. Field of the Invention
The present invention relates to a liquid crystal projection display apparatus for casting an optical image formed on a liquid crystal display element by illumination light and projecting it on a screen by a projection lens to obtain a projector image.
2. Description of the prior Art
There is known a liquid crystal projection display apparatus which is designed to place a microlens array in front of a liquid crystal display element on which an optical image is formed, converge the illumination light by a microlens to cast a corresponding pixel, and project it on a screen by enlargement with a projection lens (see Japanese Laid-open Patent Publication No. 1-189685/1989). A basic construction diagram of this kind of projection display apparatus is shown in FIGS. 3A-3B. In the figures, element 1 is a light source which generates divergent light, element 2 is a condenser lens for converting the divergent light from the light source into parallel rays; element 3' is a liquid crystal display device element 4 is a projection lens, and element 5 is a screen. In FIG. 3B there is shown a detailed view of the liquid crystal display device 3', which is constituted by a polarizer 6, a microlens array 7, a liquid crystal display element 8 and a polarizer 10. The microlens array 7 comprises the same microlenses arranged in a matrix form. The light incident on the liquid crystal display device 3' is first converted into linear polarized light by the polarizer 6, after which it is finely divided into each of the matrix-arranged pixels of the liquid crystal display element 8 with the microlens array 7, and then condensed to pass through the liquid crystal display element 8. The individual light rays are enlarged while being polarized by the liquid crystal display element 8, and only the light subjected to light modulation passes through the polarizer 10. The light emitted from the liquid crystal display device 3' is enlarged by the projection lens 4 and forms an image on the screen 5. According to this apparatus, the light once formed on the liquid crystal display element 8 is diverged to the projection lens 4, and again enlarged therefrom. Accordingly, when the liquid crystal display device and the projection lens are separated by more than a certain distance, there is a possibility for the signals of the adjacent pixels to be systematically mixed, which is systematically undesirable. Furthermore, in displaying the three basic colors of red, green and blue (R,G and B), the magnification rates thereof must be uniform. However, according to the abovementioned conventional system, it is difficult to do so.